A city is really just layers and layers of networks, placed on top of each other. And as cities modernize, those layers are becoming more and more transparent. With mobile sensors and GPS, city planners are starting to be able to get a real-time picture of all the parts of the city, moving together in a massively complex dance.

The map is made from 2,058,574 data points culled from NextBus‘s tracking system. Blue lines represent the fastest buses, going over 25 miles an hour. These are mostly routes on highways. Yellow lines show parts of routes where the buses are going 15 to 25 mph, and red shows where buses stall at less than 15 miles per hour, mostly major intersections or transit hubs.

You can see that the highway to the airport, for instance, is a speedy corridor, where buses are making excellent progress, while the crowded streets of Beacon Hill grind buses to a standstill:

Across the river in Cambridge, in Harvard Square and other commercial centers–where buses stop frequently to pick up passengers or have hubs where they wait–there’s incredible amounts of red:

As city data opens up more and more, we’re going to start seeing more interesting presentations–from experts and amateurs, alike–that make our understanding of the urban landscape much richer. And in this case, the data might help Boston’s cab drivers get richer, too.